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-rw-r--r--fs/cifs/dns_resolve.c231
1 files changed, 46 insertions, 185 deletions
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index 49315cbf742d..0eb87026cad3 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -4,6 +4,8 @@
4 * Copyright (c) 2007 Igor Mammedov 4 * Copyright (c) 2007 Igor Mammedov
5 * Author(s): Igor Mammedov (niallain@gmail.com) 5 * Author(s): Igor Mammedov (niallain@gmail.com)
6 * Steve French (sfrench@us.ibm.com) 6 * Steve French (sfrench@us.ibm.com)
7 * Wang Lei (wang840925@gmail.com)
8 * David Howells (dhowells@redhat.com)
7 * 9 *
8 * Contains the CIFS DFS upcall routines used for hostname to 10 * Contains the CIFS DFS upcall routines used for hostname to
9 * IP address translation. 11 * IP address translation.
@@ -24,214 +26,73 @@
24 */ 26 */
25 27
26#include <linux/slab.h> 28#include <linux/slab.h>
27#include <linux/keyctl.h> 29#include <linux/dns_resolver.h>
28#include <linux/key-type.h>
29#include <keys/user-type.h>
30#include "dns_resolve.h" 30#include "dns_resolve.h"
31#include "cifsglob.h" 31#include "cifsglob.h"
32#include "cifsproto.h" 32#include "cifsproto.h"
33#include "cifs_debug.h" 33#include "cifs_debug.h"
34 34
35static const struct cred *dns_resolver_cache; 35/**
36 36 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
37/* Checks if supplied name is IP address 37 * @unc: UNC path specifying the server
38 * returns: 38 * @ip_addr: Where to return the IP address.
39 * 1 - name is IP 39 *
40 * 0 - name is not IP 40 * The IP address will be returned in string form, and the caller is
41 */ 41 * responsible for freeing it.
42static int 42 *
43is_ip(char *name) 43 * Returns length of result on success, -ve on error.
44{
45 struct sockaddr_storage ss;
46
47 return cifs_convert_address(name, &ss);
48}
49
50static int
51dns_resolver_instantiate(struct key *key, const void *data,
52 size_t datalen)
53{
54 int rc = 0;
55 char *ip;
56
57 ip = kmalloc(datalen + 1, GFP_KERNEL);
58 if (!ip)
59 return -ENOMEM;
60
61 memcpy(ip, data, datalen);
62 ip[datalen] = '\0';
63
64 /* make sure this looks like an address */
65 if (!is_ip(ip)) {
66 kfree(ip);
67 return -EINVAL;
68 }
69
70 key->type_data.x[0] = datalen;
71 key->payload.data = ip;
72
73 return rc;
74}
75
76static void
77dns_resolver_destroy(struct key *key)
78{
79 kfree(key->payload.data);
80}
81
82struct key_type key_type_dns_resolver = {
83 .name = "dns_resolver",
84 .def_datalen = sizeof(struct in_addr),
85 .describe = user_describe,
86 .instantiate = dns_resolver_instantiate,
87 .destroy = dns_resolver_destroy,
88 .match = user_match,
89};
90
91/* Resolves server name to ip address.
92 * input:
93 * unc - server UNC
94 * output:
95 * *ip_addr - pointer to server ip, caller responcible for freeing it.
96 * return 0 on success
97 */ 44 */
98int 45int
99dns_resolve_server_name_to_ip(const char *unc, char **ip_addr) 46dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
100{ 47{
101 const struct cred *saved_cred; 48 struct sockaddr_storage ss;
102 int rc = -EAGAIN; 49 const char *hostname, *sep;
103 struct key *rkey = ERR_PTR(-EAGAIN);
104 char *name; 50 char *name;
105 char *data = NULL; 51 int len, rc;
106 int len;
107 52
108 if (!ip_addr || !unc) 53 if (!ip_addr || !unc)
109 return -EINVAL; 54 return -EINVAL;
110 55
111 /* search for server name delimiter */
112 len = strlen(unc); 56 len = strlen(unc);
113 if (len < 3) { 57 if (len < 3) {
114 cFYI(1, "%s: unc is too short: %s", __func__, unc); 58 cFYI(1, "%s: unc is too short: %s", __func__, unc);
115 return -EINVAL; 59 return -EINVAL;
116 } 60 }
117 len -= 2;
118 name = memchr(unc+2, '\\', len);
119 if (!name) {
120 cFYI(1, "%s: probably server name is whole unc: %s",
121 __func__, unc);
122 } else {
123 len = (name - unc) - 2/* leading // */;
124 }
125
126 name = kmalloc(len+1, GFP_KERNEL);
127 if (!name) {
128 rc = -ENOMEM;
129 return rc;
130 }
131 memcpy(name, unc+2, len);
132 name[len] = 0;
133
134 if (is_ip(name)) {
135 cFYI(1, "%s: it is IP, skipping dns upcall: %s",
136 __func__, name);
137 data = name;
138 goto skip_upcall;
139 }
140 61
141 saved_cred = override_creds(dns_resolver_cache); 62 /* Discount leading slashes for cifs */
142 rkey = request_key(&key_type_dns_resolver, name, ""); 63 len -= 2;
143 revert_creds(saved_cred); 64 hostname = unc + 2;
144 if (!IS_ERR(rkey)) {
145 if (!(rkey->perm & KEY_USR_VIEW)) {
146 down_read(&rkey->sem);
147 rkey->perm |= KEY_USR_VIEW;
148 up_read(&rkey->sem);
149 }
150 len = rkey->type_data.x[0];
151 data = rkey->payload.data;
152 } else {
153 cERROR(1, "%s: unable to resolve: %s", __func__, name);
154 goto out;
155 }
156
157skip_upcall:
158 if (data) {
159 *ip_addr = kmalloc(len + 1, GFP_KERNEL);
160 if (*ip_addr) {
161 memcpy(*ip_addr, data, len + 1);
162 if (!IS_ERR(rkey))
163 cFYI(1, "%s: resolved: %s to %s", __func__,
164 name,
165 *ip_addr
166 );
167 rc = 0;
168 } else {
169 rc = -ENOMEM;
170 }
171 if (!IS_ERR(rkey))
172 key_put(rkey);
173 }
174 65
175out: 66 /* Search for server name delimiter */
176 kfree(name); 67 sep = memchr(hostname, '\\', len);
68 if (sep)
69 len = sep - unc;
70 else
71 cFYI(1, "%s: probably server name is whole unc: %s",
72 __func__, unc);
73
74 /* Try to interpret hostname as an IPv4 or IPv6 address */
75 rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
76 if (rc > 0)
77 goto name_is_IP_address;
78
79 /* Perform the upcall */
80 rc = dns_query(NULL, hostname, len, NULL, ip_addr, NULL);
81 if (rc < 0)
82 cERROR(1, "%s: unable to resolve: %*.*s",
83 __func__, len, len, hostname);
84 else
85 cFYI(1, "%s: resolved: %*.*s to %s",
86 __func__, len, len, hostname, *ip_addr);
177 return rc; 87 return rc;
178}
179 88
180int __init cifs_init_dns_resolver(void) 89name_is_IP_address:
181{ 90 name = kmalloc(len + 1, GFP_KERNEL);
182 struct cred *cred; 91 if (!name)
183 struct key *keyring;
184 int ret;
185
186 printk(KERN_NOTICE "Registering the %s key type\n",
187 key_type_dns_resolver.name);
188
189 /* create an override credential set with a special thread keyring in
190 * which DNS requests are cached
191 *
192 * this is used to prevent malicious redirections from being installed
193 * with add_key().
194 */
195 cred = prepare_kernel_cred(NULL);
196 if (!cred)
197 return -ENOMEM; 92 return -ENOMEM;
198 93 memcpy(name, hostname, len);
199 keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred, 94 name[len] = 0;
200 (KEY_POS_ALL & ~KEY_POS_SETATTR) | 95 cFYI(1, "%s: unc is IP, skipping dns upcall: %s", __func__, name);
201 KEY_USR_VIEW | KEY_USR_READ, 96 *ip_addr = name;
202 KEY_ALLOC_NOT_IN_QUOTA);
203 if (IS_ERR(keyring)) {
204 ret = PTR_ERR(keyring);
205 goto failed_put_cred;
206 }
207
208 ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
209 if (ret < 0)
210 goto failed_put_key;
211
212 ret = register_key_type(&key_type_dns_resolver);
213 if (ret < 0)
214 goto failed_put_key;
215
216 /* instruct request_key() to use this special keyring as a cache for
217 * the results it looks up */
218 cred->thread_keyring = keyring;
219 cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
220 dns_resolver_cache = cred;
221 return 0; 97 return 0;
222
223failed_put_key:
224 key_put(keyring);
225failed_put_cred:
226 put_cred(cred);
227 return ret;
228}
229
230void __exit cifs_exit_dns_resolver(void)
231{
232 key_revoke(dns_resolver_cache->thread_keyring);
233 unregister_key_type(&key_type_dns_resolver);
234 put_cred(dns_resolver_cache);
235 printk(KERN_NOTICE "Unregistered %s key type\n",
236 key_type_dns_resolver.name);
237} 98}
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